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Clarence  Mo  ores  Weed 


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L.  B.  Cat.  No.  1137 


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The  Winged  Travellers  of  the  Milkweed. 
Drawn  by  James  Hall. 


Seed-Travellers 


Studies  of  the  Methods  of  Dispersal  of 
Various  Common  Seeds 


BY 


CLARENCE  MOORES   WEED 


BOSTON,  U.S.A. 
GINN    &    COMPANY,  PUBLISHERS 

1899. 


Copyright,  1898,  by 
CLARENCE  MOORES  WEED 

/iLL    RIGHTS    RESERVED 


INTEODUCTIOI^. 


There  are  few  subjects  better  adapted  to  awakening  the 
faculties  of  observation  to  a  sense  of  the  significance  of  those 
things  in  the  living  world  with  which  we  come  in  daily  contact 
than  that  of  the  dispersal  of  seeds.  Away  from  the  crowded 
streets  of  cities  one  can  scarcely  step  out  of  doors  without  wit- 
nessing some  phase  of  plant  dispersal,  while  a  little  intelligent 
attention  to  the  commonest  objects  along  the  roadside  will  reveal 
numberless  interesting  facts. 

These  studies  may  be  pursued  to  advantage  at  any  season  of 
the  year,  but  there  is  an  especial  wealth  of  material  during  the 
months  of  autumn  and  winter. 

For  studies  of  nature  in  the  schools,  seeds  and  fruits  are  par- 
ticularly desirable.  Specimens  illustrating  the  various  methods 
of  dispersal  are  easily  obtained  by  the  pupils  themselves.  The 
significance  of  the  several  adaptations  to  dissemination  is  at 
once  apparent ;  the  connection  between  the  plant  and  its  sur- 
roundings is  shown  to  advantage  ;  and  the  general  idea  of  the 
unity  of  nature  may  readily  be  brought  before  attentive  minds. 

I  would  recommend  that  this  little  book  be  used  in  connec- 
tion with  observations  upon  the  specimens  treated  of  ;  that  the 
studies  be  read  by  the  individual  pupils,  either  with  the  objects 
in  hand  or  for  the  purpose  of  inciting  them  to  search  for  the 
specimens.  If  the  material  does  not  present  itself  in  the  order 
of  the  studies  as  they  appear  in  the  book,  the  studies  may  be 
read  in  the  order  in  which  the  specimens  are  ol)tained.     It  may 


iv  INTllODUCTION. 

then  be  advisable,  after  most  of  the  parts  have  been  read,  to 
review  the  whole  subject  by  having  the  pupils  begin  at  the  first 
of  the  book  and  read  it  through  consecutively,  with  or  without 
studying  the  objects  again.  They  will  thus  be  given  a  logical 
idea  of  the  subject  as  a  whole,  and  the  knowledge  already  gained 
will  be  more  firmly  fixed  in  their  minds. 

To  the  teacher  about  to  take  up  the  subject  of  seed  dispersal 
I  would  commend  the  spirit  of  these  lines,  written  some  years 
ago  by  Prof.  L.  H.  Bailey :  "  The  studious  observer  of  nature 
is  constantly  impressed  with  the  unlimited  numbers  of  curious 
little  contrivances  and  peculiar  habits  by  means  of  which  the 
commonest  plants  and  animals  are  prepared  to  overcome  the 
obstacles  which  surround  them,  for  be  it  known  that  even  plants 
have  obstacles  to  surmount  if  they  perpetuate  their  species.  A 
plant  must  hold  its  own  against  its  stronger  and  more  aggressive 
neighbors,  or  suffer  the  fate  of  many  of  our  native  plants,  which 
have  been  diiven  out  by  Old  World  weeds  ;  it  must  possess 
some  means  of  scattering  its  seeds  beyond  the  limits  of  severe 
competition  ;  it  must  struggle  against  uncongenial  climate  and 
the  ruinous  changes  wrought  by  man  ;  and  it  must  elude  or 
repel  the  attacks  of  herbage-loving  or  seed-loving  animals.  One 
Avho  is  interested  in  the  fascinating  peculiarities  of  common 
objects  is  often  pained  by  the  sneering  estimate  put  upon  them 
by  less  observant  j)eople.  No  one  is  prepared  to  study  nature 
so  long  as  he  regards  any  phenomenon,  however  slight  in  itself, 
as  trivial  and  unworthy  his  regard.  He  must  not  attempt  to 
play  the  critic  with  nature.  He  must  assume  the  attitude  of  a 
patient  learner,  who  accepts  all  things  as  worthy  his  study  and 
consideration."  ^ 

C.  M.  W. 

^  Talks  Afield  about  Plants. 


CO^TEI^TS. 


PART  L  — THE   WIND   AS   A   SEED   DISTRIBUTER. 

PAGE 

On  the  Wings  of  the  Wind      -------  1 

The  Cat-tail  Flag -        -        -10 

Key-fruits,  or  Samaras      -- 13 

Fly-away  Grass  and  Tumble-weeds -     18 

The  Russian  Tumble-weed  --.----21 

Sliding  on  the  Snow      - --24 

Sailing  on  Still  AVaters  --------26 

PART  IL  — SEED   DISSEMINATION   BY   BIRDS. 

Travelling  with  the  Birds          -- 29 

Wild  Cherries     - 33 

The    Pokeberry,  or  Pokeweed     - 35 

The  Barberry      ---- 38 

The  Poison  Ivy  and  the  Harmless  Sumachs    -        -        -        -  40 

PART  III.  — SEED  DISPERSAL  BY   SPINES   AND   HOOKS. 

The  Burr  Marigold  and  the  Hooked  Crowfoot  -        -        45 

The  Burdock  and  the  Clotburr  ------    49 


SEED-TEA  YELLEES. 


PAET   I.  — THE   WIND   AS   A   SEED   DISTEIBUTER. 


ON  THE  WINGS   OF  THE   WIND. 

Every  one  who  has  wandered  along  a  country  road  has 
noticed  the  peculiar  seed  pods  of  the  common  milkweed, 
represented  in  the  frontispiece.  About  midsummer  you  may 
see  them  forming  as  slender  green  cases,  which  increase 
rapidly  in  size.  During  the  latter  part  of  summer  they  change 
from  green  to  brown,  gradually  drying  out  as  the  Aveeks  go  by. 
Finally  they  ripen  and  split  open  along  one  side. 

As  the  pods  open  there  is  revealed  a  large  number  of  flat- 
tened brown  seeds,  having  the  margins  thinner  than  the  middle 
portions.  When  the  pod  is  wide  open  you  may  see  that  the 
seeds  overlap  in  a  manner  suggestive  of  the  shingles  on  a 
house.  The  ends  onlj^  of  most  of  them  can  be  seen.  Those 
at  the  tip  of  the  pod,  however,  are  visible  throughout  their 
length.  They  show  that  each  seed  bears  on  its  smaller  end 
a  tuft  of  silken  hairs.  When  the  pod  first  opens  these  hairs 
lie  straight  and  flat,  the  ends  of  the  hairs  being  caught  in 
the  folds  of  the  membranous  partition  which  runs  through 
the  center  of  the  pod. 

On  exposure  to  the  air  the  folds  relax  their  hold  upon  the 

hairs,  which  thus  become  free  at  their  upper  ends.     Then  each 

1 

PROPERTT  LIBRARY 


THE    WIND    AS    A   SEED   DISTRIBUTER.  6 

hair  curls  over  toward  the  other  end  of  the  seed,  until  at 
last  nearly  all  the  hairs  on  the  upper  seeds  are  thus  curled 
over,  forming  a  beautiful  crown,  almost  as  light  as  air.  When 
a  strong  wind  blows,  the  seeds  are  picked  up  by  means  of  these 
hairs  and  carried  away  to  be  dropped  beside  some  fence  or  ti-ee 
or  bush. 

By  the  beautiful  device  of  this  feathery  crown  the  milk- 
Aveed  provides  for  the  scattering  of  its  seeds.  It  seems  a 
simple  process,  but  as  you  think  it  over  you  see  that  it  is 
a  very  admirable  one.  It  is  well  worth  while  to  bring  to  the 
schoolroom  two  or  three  of  the  nearly  ripened  pods  and  place 
them  beside  a  sunny  window,  or  on  a  desk  in  some  other  part 
of  the  room.  As  the  pods  dry  they  crack  o|)en ;  the  seeds 
become  loosened;  the  white  threads  curl  up.  There  being  no 
wind  to  carry  the  seeds  away,  they  form  a  fluffy  white  mass, 
with  brown  spots  where  the  seeds  show.  Blow  upon  the 
mass  and  see  how  easily  the  tiny  balloons  are  wafted  away. 

The  long,  slender,  decorative  seed  pods  of  the  spreading 
dogbane  or  Indian  hemp,  a  plant  closely  related  to  the  milk- 
weed, give  forth  their  beautiful  little  seeds  in  a  similar  way 

(Fig-  !)• 

Another  example  of  this  method  of  seed  dispersal  is  found 

in  the  common  fireweed  or  willow  herb.  The  seeds  are 
produced  in  long  pods,  which  when  mature  split  from  above 
downward  into  four  longitudinal  divisions,  each  of  Avhich  curls 
back  and  exposes  the  achenes  to  the  air.  Each  achene  is  pro- 
vided with  a  mass  of  tiny  white  hairs  on  its  upper  end.  As 
the  air  reaches  these  they  expand  into  parachutes,  become 
separated,  and  sail  away  (Fig.  2). 

The  seeds  of  Avillow  and  poplar  are  covered  with  white 
downy  silk,  by  means  of  which  they  are  borne  through  the  air 
in  summer,  often  so  filling  it  as  to  suggest  a  light  snowstorm. 


4  SEED-TKAVELLERS. 

Of  course,  plants  which  rely  upon  the  wind  for  the  dispersal 
of  their  seeds  have  to  take  their  chances  that  the  seeds  will 
find  lodgment  under  conditions  favorable  to  growth.  A  large 
majority  of  the  seeds  must  be  lost  and  never  develop  into 
plants.  But  so  many  seeds  are  produced  that  if  only  a  small 
proportion  are  successful,  the  plant,  as  a  species,  will  flourish. 


Fig.  2.  —  Seed  Pods  of  Fireweed. 


The  family  that  as  a  whole  has  most  availed  itself  of 
the  seed-carrying  properties  of  the  winds  is  the  Composite 
family,  —  the  great  order  of  plants  with  flowers  in  heads, 
of  which  the  thistle,  sunflower,  dandelion,  and  daisy  are 
familiar  examples. 


,(»vVi*^^jj^ 


Fig.  3.  —  The  Common  Thistle.    (After  Vasey.) 


6 


SEED-TRAVELLEKS. 


This  adaption  to  wind  dispersal  is  beautifully  shown  in  the 
seed-heads  of  the  common  pasture  thistle.  The  seeds  —  which 
the  botanist  calls  the  achenes  —  are  borne  in  the  familiar  spiny 
flower  cups  which  spread  apart  as  they  ripen  and  dry.      On 


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Fig.  4.  —  Seeds  of  Golden-rod. 


the  top  of  each  achene  is  a  crown  of  slender,  white,  plumose 
bristles,  which,  on  exposure  to  the  air  by  the  spreading  flower 
head,  expand  more  and  more,  until  finally  the  bristles  are 
spread  as  a  tiny  parachute.  Then  each  escapes,  taking  with 
it  the  seed. 


THE    AYIND    AS    A    SEED    DISTRIBUTER. 


Fig.  5.  —  Golden-rod  Seed,  showing 
Pappus  and  Withered  Flower. 


This  escape   is  most  likely  to  take   place   during  a  drying 

wind,  when  the  seeds  will  be  carried  with  the  breeze.     They 

may  go  far  before  striking  anytliing ; 
but  should  they  be  blown  against  a 
fence  or  wall  or  stump,  the  seeds 
separate  from  the  parachute  and 
drop  to  the  ground. 

The  plumose  bristles  which  form 
the  parachute  of  the  thistle  seed 
represent  the  divisions  of  the  sepals^ 
which  every  schoolboy  nowadays 
knows  form  the  calyx  or  outer 
covering    of    the    simple    flowers. 

When  the  calyx  is  modified  in  this  way  it  is  usually  spoken 

of  as  the  pappus.  The  carry- 
ing power  of  the  thistle  pap- 
pus is  greatly  increased  by  the 

numerous    plumose    branches 

along  each  division. 

The  fact  that  the'  pappus  is 

the  modified    calyx    is    easily 

seen  by  examining  with  a  lens 

the   newly  ripened    seed-head 

of     an    aster     or    golden-rod 

(Fig.  4).    You  will  notice  that 

the  withered  corolla    of  each 

flower,  enclosing  the  stamens 

and  stigma,  is  still  in  position 

with  the  limbs  of  the  pappus 

surrounding    it    at    the    base 

(Fig.    5).       At    the    slightest 

touch    the    corolla     breaks    off,  fig,  O.  —  Seed-heads  of  Dandelion. 


8 


SEED-TRAVELLERS . 


leaving  simply  the  seed  surmounted  by  the  pretty  expanded 
ring  of  white  bristles. 

The  seed-heads  of  the  aster  and  golden-rod  are  small,  so  that 
there  is  room  for  the  expansion  of  the  pappus  on  the  rather 
short  seeds. 

The  dandelion  (Fig,  6)  shows  a  slight  modification  of  the 
seed  structure  prevailing  in  most  compound  flowers.  The 
pappus,  instead  of  springing  directly  from  the  top  of  the  seed, 
is  borne  on  the  end  of  a  long  "  beak  "  formed  by  the  lengthen- 


FiG.  7.  —  Seeds  of  Dandelion. 

ing  of  the  tip  of  the  ovary.  One  advantage  of  this  is  to  be 
found  in  the  fact  that  by  thus  enlarging  what  we  may  call 
the  circumference  of  expansion,  the  jjappus  of  all  the  achenes 
finds  room  to  expand.  Were  the  pappus  attached  directly  to 
the  top  of  the  ovary,  there  would  be  a  very  crowded  condition 
of  things  when  the  silken  tufts  attempted  to  spread  out. 

After  the  ovules  of  the  dandelion  have  been  fertilized  the 
seed-head  closes  up,  remaining  in  this  condition  until  the  seed 
ripens.  Meanwhile  the  beaks  on  the  ovaries  lengthen  and 
the  flower  stalk   grows  longer,  pushing  the  seed-head  above 


THE    WIND    AS    A    SEED    DISTRIBUTER.  U 

the  surrounding  grass,  where  the  ripened  seeds,  with  the  pappus, 
assume  the  form  of  a  ghostly  sphere  and  are  picked  up  by 
the  wind  to  be  wafted  far  and  wide. 

If  you  examine  the  achene  of  the  dandelion  you  will  find 
its  outer  surface  roughened  by  projecting  points.  By  means  of 
these,  when  once  it  lodges  in  the  ground  it  is  securely  anchored 
in  place. 


THE   CAT-TAIL  FLAG. 


No  plant  adds  a  more  decorative  effect  to  the  scenery  along 
the  margins  of  lakes  and  ponds  than  that  which  is  familiarly 
known  as  the   "cat-tail"  or  "cat-tail  flag,"  though  sometimes 


Fig. 


The  Home  of  the  Cat-tail  Flag. 


called   the  bulrush,  and  occasionally  known  by  its  botanical 
name,  Typha. 

The  long,  flat,  straight,  light-green  leaves  of  this  plant  pro- 
ject obliquely  upward  above  the  water,  on  each  side  of  the 
straight,  smooth,  cylindrical  leaf-stalk,  crowned  with  the  larger 
cylinder  of  the  brown  seed-mass.     The  grace  of  this  in  turn  is 


10 


THE    WIND    AS    A    SEP^D   DISTKIBUTER. 


11 


emphasized  by  the  smaller,  more  steeple-like  stem  that  projects 
above  it.  The  whole  forms  a  charming  study  in  a  simple  decora- 
tive design,  the  beauty  of  which  artists  have  long  appreciated. 
The  plant  is  equally  interesting  to  the  botanical  student. 
From  our  present  point  of  view  it  is  well  worth  while  to  pick 


Fig.  9.  —  Seeds  of  the  Cat-tail  Flag. 

off  a  little  of  the  brown  fuzz  from  the  stalk  and  examine  it 
under  a  simple  lens.  If  you  pull  out  a  tiny  bunch  from  a 
seed-head  which  has  not  yet  begun  to  expand,  you  will  see  at 
first  that  the  bunch  consists  of  a  great  number  of  slender  stalks, 
each  of  which  has  numerous  small  white  hairs  arising-  alonor  its 
surface  and  lying  parallel  with  it  (Fig.  9,  a). 


12  SEED-TRAVELLERS. 

But  soon  after  you  have  removed  the  mass  to  a  table  or  the 
stage  of  a  simple  microscope  you  will  see  it  gradually  become 
fluffy,  and  it  will  soon  occupy  many  times  the  space  it  did  at 
first.  Look  carefully  now  and  you  will  see  that  each  of  the 
little  side  branches  instead  of  lying  parallel  with  its  stem  is  at 
right  angles  to  it.  On  the  tiny  stem  above  these  hairs  is  a 
little  oval  brown  body  which  contains  the  seed  (Fig.  9,  h). 
The  stem  mentioned  is  the  stalk  of  the  fruit,  so  that  in  this 
case  the  parachute  is  developed  on  the  stalk  below  the  ovary, 
instead  of  above  as  with  the  dandelion  and  other  plants.  BIoav 
gently  upon  the  fluffy  mass  and  see  how  the  seeds  scatter. 

You  are  now  in  position  to  appreciate  better  the  meaning  of 
the  masses  of  "  cat-tails  "  to  be  found  by  the  side  of  nearly 
every  pond.  All  through  the  winter  the  brown  seed-masses 
project  above  the  ice  and  snow,  where  they  are  visited  by  many 
seed-eating  birds  which  peck  the  heads  apart.  Thus  exposed 
to  the  air  the  tiny  parachutes  open,  forming  great  fluffy  masses 
that  are  taken  up  by  the  Avind  and  scattered  in  every  direction. 
Of  course  the  vast  majority  of  them  will  never  be  carried  to 
places  favorable  to  their  growth,  but  a  few  are  almost  certain 
to  reach  the  borders  of  ponds  or  swamps,  where  suitable  con- 
ditions exist.  If  you  attempt  to  estimate  the  number  of  seeds 
in  a  single  head  you  will  be  convinced  that  if  only  one  seed 
in  ten  thousand  grows,  the  plant  will  be  able  to  multiply 
rapidly. 

In  case  birds  do  not  peck  at  the  heads,  they  finally  are 
broken  open  by  the  action  of  the  wind  and  weather,  and  the 
seeds  are  scattered  in  a  similar  way. 


KEY-FRUITS,    OR   SAMARAS. 

There  are  many  methods  by  which  seeds  have  been  adapted 
to  dispersal  by  the  wind.  The  degree  of  adaptation  is  greatly 
varied.  With  the  fruits  of  many  trees  the  seed-envelopes  have 
been  drawn  out  into  thin  plates,  by  means  of  Avhich  in  a  strong 
^yind  —  when  of  course  they  are  most  likely  to  Ijreak  away 
from   the  stem  —  they  may  be   carried  to  a  considerable   dis- 


FiG.  10.  —  Maple  Keys. 

tance  before  falling  to  the  ground.     Even  then  during  liigh 
winds  many  of  them  will  be  picked  up  and  carried  farther. 

The  familiar  fruits,  or  ''keys,"  of  maple  (Fig.  10)  and  ash  at 
once  come  to  mind  as  examples  of  this  kind  of  dispersal.  It 
is  to  be  noted  that  generally  in  such  cases  the  seed  lias  a 
decided  advantage  in  starting  at  a  point  some  distance  from 
the  ground.     Its  chances  of  going  far  afield  are  much  greater 

13 


14 


SEED-TRAVELLERS. 


than  they  would  be  if  the  seed  was  borne  on  a  herbaceous  plant 
only  a  foot  or  two  high. 

Botanically  speaking,  the  object  which  is  commonly  called 
the  seed  of  maple,  ash,  or  elm  is  really  a  fruit.  While  most 
of  us  think  of  an  edible  pear  or  apple,  peach  or  grape,  when 
the  word  fruit  is  brought  to  mind,  it  means  to  the  botanist 
simply  "the  seed-bearing  product"  of  a  plant,  whether  edible 
or  not. 

If   you   examine,   for  instance,   the  familiar 
seeds  "  of  the  elm,  you  will  find  in  the  center 
a  tiny  object  which  is  the  seed  proper.     The 
brownish  or  greenish  outer  cover- 
ing is  the  developed  ovary,  or 
the  envelope  in  which  the  minute 
ovule  was  borne  in  the  blossom. 
In  this  case  the  margin  of  the 
ovary  has  been  drawn  out  all 
around  into  thin  plates,  mak- 
ing a  tiny 
parachute, 
which    in 
a    strong 
wind    will 

sail    some    distance   in   the    air   before    reaching  the  ground. 
Such  a  winged  fruit  is  often  called  a  samara,  or  key-fruit. 

The  hop  tree,  or  shrubby  trefoil,  has  a  similar  but  larger 
fruit  (Fig.  11)  with  two  little  black  seeds  in  the  swollen  center. 
This  is  a  two-celled  samara,  with  each  ovary  having  one-half 
of  its  margin  drawn  out,  and  the  two  united  in  such  a  way 
as  to  give  an  appearance  very  similar  to  that  of  the  seed  of 
the  elm. 

In  the  case  of  the  ash,  the  fruit,  instead  of  having  wings  all 


Fig.  11.  —  Key-fruits  of  Hop  Tree. 


THE    WIND    AS    A    SEED    DISTKIBUTER. 


15 


around,  has  a  wing  at 
being  held  in  pockets 
fruit  of  the  maple  is  a 
base,    with    the    wings 
Many    people    have 
the  plates  spread  wide 
formed  they  are  closely 
you  gather  one  of   the 
over  a  table   in  a  warm 
will  notice  that  the  plates 
still  later   you  will    find 
small     brown     winged 
the  seeds  of  the  pine 
doors,  the  seeds,  in- 


the  tip  end  only,  the  seeds  proper 

at  the  basal  end  (Fig.  12).     The 

two-keyed  samara,  joined  at  the 

developed  along  the  outer  edges. 

noticed  that  old  pine  cones  have 

apart,  while  in   those  recently 

appressed.     If    in    autumn 

slender  cones  and  hang    it 

room,  a  few  days  later  you 

are   spreading    open,    and 

on    the    table   a  number  of 

seeds    (Fig.    13).     These  are 

Had    the    cone    been    out   of 

stead    of    dropping    straight 


Fig.  12.  — Key -fruits  of  Ash. 


downward,  would  have  been 
wafted  away  some  distance 
by  the  wind.  The  cones  with 
their  seeds  do  not  mature 
until  the  second  autumn 
after  the  blossom  was  pro- 
duced. 

This  development  of  wings 
upon  the  seeds  or  seed-cover- 
ing is  not  confined  to  trees 
and  shrubs.  Many  herbaceous 


Fig.  13.  — Seeds  of  Pine. 


Fig.  14.  —  Leaf  and  Fruits  of  Yellow  Dock.    (After  Vasey.) 


THE    WIND    AS    A    SEED    DISTRIBUTER.  17 

plants  have  also  adopted  it,  although  in  such  cases  the  fruits 
are  generally  smaller  than  those  of  trees.  A  familiar  example 
is  found  in  the  common  yellow  dock,  represented  in  Fig.  14. 
If  you  examine  the  fruits  this  plant  produces  so  profusely  in 
summer  and  autumn,  and  to  be  found  more  or  less  abundantly 
through  the  winter  months,  you  will  see  that  the  seed- 
covering  is  developed  into  thin  plate-like  margins,  wliich 
greatly  increase  the  surface  exposed  to  the  wind. 


FLY-AWAY   GRASS  AND   TUMBLE-WEEDS. 

One  breezy  October  morning  the  neighboring  fields  pre- 
sented the  appearance  of  a  fairies'  carnival.  A  thousand 
tenuous  will-o'-the-wisps  were  dancing  and  sailing  and  whirl- 
ing in  every  direction.     Now  one  alone  with  feathery  grace 


--fFi; 


Fia.  15.  —  Head  of  Fly-away  Grass. 

would  glide  along,  to  join  a  moment  later  a  host  of  airy  s^Drites, 
and  be  wafted  hither  and  thither  by  the  erratic  breath  of  the 
zephyr  god.  Here  and  there  the  paths  of  miniature  cyclones 
could  be  traced  by  the  movements  of  whirling  circles,  while 
in  other  places  solid  j)halanxes  moved  steadily  forward.     The 

18 


THE    WIND    AS    A    SEED    DISTRIBUTER.  19 

ranks  of  the  revellers  were  constantly  depleted  through  deser- 
tions to  the  eastward,  to  be  quickly  filled  by  new  recruits 
from  out  the  west. 

With  some  difficulty  I  caught  a  few  of  these  feathery  sprites, 
and,  holding  them  securely,  started  homeward.  But  a  sudden 
gust  of  wind  left  me  empty-handed,  save  for  some,  tiny  pieces 
of  stems ;  the  sprites,  again  at  liberty,  sailed  away  with  mocking 
grace.  I  caught  more,  and,  shielding  them  from  the  Avind,  got 
them  safely  indoors,  where  they  proved  to  be  the  seed-heads  of 
a  grass  commonly  known  as  the  "  old-witch  grass." 

The  seeds  of  this  plant  are  produced  in  a  long,  wide-spread- 
ing head  (Fig.  15)  called  by  botanists  a 
paiiicle.  The  lower  branches  of  the  panicle 
curve  downward,  while  the  upper  ones 
curve  upward,  thus  giving  to  the  panicle 
as  a  whole  a  rounded  outline  well  adapted 
to  rolling  along  the  ground.    The  branches 

are  joined  to  the  stalk  by  thickened  braces  fig.  le.- joints  of  oid-witch 
(Fig.  16),  making  the  union  much  firmer      Grass,  showing  braces : 

,1  'i       Ji  •  111  ^,  lower  branch : 

than  It  otherwise  would  be.  j,^  ^^^,p^^.  y,,^,,,,^,,_ 

The  stem  below  the  panicle  is  very 
brittle.  As  soon  as  the  seeds  are  thoroughly  ripened  the  stem 
becomes  dry  and  is  broken  off  by  the  wind.  The  seed-head  is 
then  wafted  away  until  stopped  by  some  obstacle.  The  seeds, 
held  in  tiny  pockets  at  the  tip  of  the  branches,  drop  out  on  the 
way,  so  that  the  panicle  scatters  them  all  along  its  path. 

The  old-witch  grass  has  thus  adopted  a  most  efficient  method 
of  seed  distribution.  Out  of  the  hundreds  of  seeds  sown  broad- 
cast by  every  whirling  panicle,  some  are  pretty  sure  to  find 
the  right  conditions  for  growth. 

This  old-Avitch  grass,  or  ''fool  hay"  as  it  is  sometimes  called, 
may  serve  to  illustrate  the  method  adopted  by  a  large  number 


20  SEED-TRAVELLERS. 

of  plants  for  the  dispersal  of  their  seeds.  Other  grasses, 
notably  the  fly-away  grass,  have  taken  advantage  of  it,  as  well 
as  many  of  our  most  noxious  weeds. 

The  various  tumble-weeds  derive  their  common  name 
from  the  habit  of  tumbling  or  rolling  along  the  ground  when 
the  wind  is  blowing,  scattering  far  and  wide  their  myriad 
seeds.  These  plants  usually  have  an  oval  or  spherical  outline, 
and  the  stem  breaks  off  above  the  root  after  the  ripening  of 
the  seed.  One  of  the  most  familiar  examples  is  the  common 
tumble-weed  of  waste  grounds,  —  the  Amaranthus  alhus  of 
botanists. 

In  the  great,  unbroken  sweep  of  the  prairies  the  tumble- 
weeds  are  especially  at  home.  In  such  regions  they  flourish 
much  more  than  in  hilly  or  mountainous  localities,  because  of 
the  comparatively  few  obstacles  to  prevent  their  wide  dispersal. 


THE   RUSSIAN  TUMBLE-WEED. 

About  twenty  years  ago  a  colony  of  immigrants  brought 
from  the  plains  of  southern  Russia  to  the  prairie  region  of 
Dakota  a  small  quantity  of  flaxseed. 

The  flaxseed  was  sown  in  the  fertile  soil  of  the  new  home. 
It  sprouted  and  grew.  Along  with  it  there  also  developed  a 
slender,  reddish  plant  Avhich  seemed  natural  enough  to  the 
immigrants,  for  it  had  been  commonly  present  in  the  crops  on 
the  far-away  prairies  from  Avhence  they  came. 

The  slender,  reddish  plants  waxed  strong  and  as  they  grew 
older  broadened  out,  becoming  harsh  and  spiny.  When  the 
flax  was  harvested  the  spiny  plants  were  probably  left  in  the 
field.  They  Avere  not  useful  to  the  flax  crop,  and  in  the  den- 
sity of  his  ignorance  one  could  not  expect  the  immigrant  to 
see  in  those  scattered  plants  a  menace  of  tremendous  import  to 
American  agriculture.  The  eyes  of  others  were  equally  blind. 
The  following  season  more  plants  came  up,  and  so  the  species 
continued  to  multiply  year  after  year. 

This  plant  first  appeared  in  a  locality  which  was  wooded  and 
hilly,  but  in  a  few  seasons  it  reached  the  adjacent  plains,  where 
it  was  rolled  by  the  wind  for  miles  and  miles,  each  j^ear  after- 
ward invading  new  territory.  Within  a  dozen  years  it  had 
spread  throughout  South  Dakota,  had  entered  North  Dakota 
on  the  south,  Iowa  on  the  north,  and  Nebraska  on  the  east. 
During  the  next  few  years  it  spread  with  marvellous  rai)idity, 
invading  Minnesota,  Wisconsin,  Colorado,  Illinois,  and  (^liio. 
Its  progress  was  aided  by  tlie  railroads  that  carried  the  seed  to 
many  distant  localities,  which  quickly  became  new  centers  of 
distribution.     Presumably  the  plant  will  continue  to  spread  by 


22  SEED-TRAVELLERS. 

similar  methods,  and  within  a  few  years  will  be  present  in  most 
of  the  United  States. 

Such  is  the  past  history,  so  far  as  it  can  be  traced,  of  the 
plant  commonly  called  Russian  thistle  or  Russian  cactus  (Fig. 
17),  although  it  is  neither  a  thistle  nor  a  cactus.  More  appro- 
priately it  is  sometimes  spoken  of  as  the  Russian  tumble-weed. 
Botanically,  it  is  a  saltwort,  being  considered  merely  a  variety 


''""vV^^i^ 

;  5  iiVj. 

4 

L 

;_,.-.. 

v'^'^iSMfl 

i 

^H 

HM^n^ 

'   H- 

'.^^•s! 

mM 

^m 

■IP 

^^ 

^ 

,' 

1 

1 

^p^:^^*T 

i. 

1 

'^^Ic'^nI 

^^1 

^^^^H 

^l/-     . , 

•r    ^S^^ 

sai«i*r.  ■^s|. 

''•^H 

BSs^A^^'' 

1 

1 

n 

mmKMm^m^ 

■ 

p 

#" 

Fig.  17.  —  The  Russian  Thistle.    (From  Selby.) 

of  the  saltwort  common  along  our  Atlantic  coast,  as  well  as  in 
many  parts  of  Europe. 

In  the  plains  region  of  southeastern  Russia  this  plant  has 
long  been  known  as  a  noxious  pest.  On  its  account  "  the  cul- 
tivation of  crops  has  been  abandoned  over  large  areas  in  some 
of  the  provinces  near  the  Caspian  Sea."  In  our  own  west  it 
has  already  caused  damage  amounting  in  a  single  state  to  mil- 
lions of  dollars  a  year. 


THE    AVIND    AS    A    SEED    DISTRIBUTER. 


23 


The  Russian  thistle  begins  its  yearly  growth  in  a  simple, 
inoffensive  way.  The  young  plants  are  slender  and  succulent, 
but  as  they  grow  older  they  harden  and  spread  out,  becoming 
densely  covered  with  sharp  spines.  When  full  grown  they 
often  reach  a  diameter  of  four  or  five  feet,  a  majority  of  the 
specimens   being    distinctly   rounded    in    outline.      After    the 


Fig.  18.  —  Young  Russian 
Tumble-weed. 
(After  Dewey.) 


Fig.  19.  —  Ku.ssian  TnniMc-weed  : 
a,  part  of  branch,  natural  size  ;    h,  flower  hchl  by  threads 
as  in  the  rolling  plant,  magnified  ;  f,seed,  magnified. 
(After  DicwEV.) 


seeds  have  matured  the  stem  twists  around  and  breaks  off,  thus 
leaving  the  plant  to  roll  wherever  the  wind  blows  it,  dropping 
its  seeds  as  it  goes  along.  As  one  large  \)\^nt  sometimes  pi-o- 
duces  200,000  seeds,  and  may  be  blown  for  miles,  one  can 
readily  imagine  how  soon  a  prairie  region  miglit  be  overrun 
by  the  pest,  which  grows  so  vigorously  that  it  crowds  out 
practically  all  plants  with  which  it  comes  in  competition. 


SLIDING   ON  THE   SNOW. 

For  a  long  period  of  each  year  in  our  northern  regions  the 
earth  is  covered  with  a  mantle  of  snow  which  often  becomes 
coated  with  a  crust  of  ice.  When  this  happens  there  is  pro- 
duced a  smooth,  slippery  surface  across  which  small  objects 
readily  slide  before  the  wintry  winds. 

This  snowy  crust  is  an  important  aid  in  the  dispersal  of 
many  seeds.  The  seed-bearing  branches  of  many  of  our  com- 
monest plants  project  above  the  snow,  where  they  are  visited 
by  winter  birds  that  come  to  feed  upon  the  seeds.  But  the 
birds  scatter  nearly  as  many  as  they  devour.  When  the  snowy 
surface  holds  the  seeds  from  falling,  the  latter  are  in  position 
to  be  diiven  over  the  surface  by  the  wind.  If  there  is  an  icy 
crust  they  are  likely  to  go  alone ;  if  not,  they  ma}^  be  carried 
with  the  drifting  snow. 

While  this  method  of  seed  dispersal  is  universal  throughout 
our  northern  states,  it  operates  most  freely  in  the  plains  regions 
of  the  west  and  northwest.  To  determine  how  effective  this 
means  of  dispersal  is,  Prof.  H.  L.  Bolley  of  North  Dakota 
recently  performed  the  following  experiment.  On  Jan.  31, 
1895,  when  there  was  a  light  snowfall  upon  crusted  snow, 
with  the  Avind  constant  from  the  northwest  at  the  rate  of 
twenty  miles  an  hour,  a  peck  of  mixed  seed  was  poured  upon 
the  crust.  Thirty  rods  distant,  at  right  angles  to  the  course 
of  drifting,  a  three-inch  trench  in  the  snow,  four  rods  long, 
served  to  catch  the  drifting  seeds.  At  the  end  of  ten  minutes 
the  trench  was  found  to  contain : 


1  rc^d  'z    Sya 

24 


CMlp0e 


TKE    WIND    AS    A    SEED    DISTUIIUiTEll.  25 

Millet  seed Very  many  seeds. 

Wheat 101      " 

Flax 58     " 

Buckwheat    .     ,     .     .     • 415     " 

Ragweed        91     " 

Similar  experiments  were  made  at  other  times,  and  the  con- 
clusion was  reached  that  ''  weed  seeds  of  almost  any  size,  as 
French-weed,  Russian  cactus,  or  ragweed,  may  travel  with  the 
drifting  snows  many  miles  during  heavy  storms,  settle  down 
into  the  snow,  and  there  be  buried  in  the  soil  upon  the  melting 
of  the  snow." 

You  may  often  observe  a  similar  process  of  seed  distribution 
on  ponds  in  winter.  On  the  side  of  the  pond  away  from  the 
direction  of  the  prevailing  wind  there  will  be  found  Avindrows 
of  seeds  of  sedges  and  other  plants  that  have  been  blown  upon 
the  ice  across  the  pond. 


SAILING   ON   STILL  WATERS. 

The  problems  of  existence  which  plants  have  to  solve  are 
innumerable.  Wherever  they  grow  they  must  so  adapt  them- 
selves to  surrounding  conditions  that  they  shall  derive  the 
greatest  benefit  with  the  least  expenditure  of  vital  force. 

Different  situations  require  different  adaptations.  Those 
plants  which  have  adopted  as  their  home  the  quiet  borders  of 
the  stagnant  pool  or  the  inland  lake,  the  reedy  marsh  or  the 
slow-running  creek,  have  to  fulfill  the  conditions  of  existence 
by  methods  very  different  from  those  employed  by  the  plants 
of  the  hillside  and  wayside.  In  the  problem  of  the  latter,  as 
far  as  seed  dispersal  is  concerned,  the  air,  the  bird,  or  the  beast 
are  the  factors  chiefly  to  be  considered,  but  the  solution  of  the 
problem  of  the  former  depends  largely  upon  adaptation  to  the 
surrounding  water. 

The  ways  in  which  the  seeds  of  water  plants  are  adapted  to 
dispersal  may  well  be  illustrated  by  three  groups  found  every- 
where in  the  vicinity  of  standing  water,  —  the  sedges,  the 
arrow-leaf  plants,  and  the  water  lilies. 

The  most  abundant  plants  in  marshes  and  by  pondsides  are 
the  sedges.  They  resemble  coarse  grasses,  for  which  they  are 
frequently  mistaken.  Some  of  them  have  seeds  adapted  to 
wind  dispersal  by  means  of  cottony  tufts  of  hairs ;  but  most  of 
them  simply  cast  their  seeds  upon  the  quiet  waters,  where  they 
float  upon  the  surface  and  are  driven  along  by  every  breath  of 
wind. 

It  will  be  worth  your  while  to  remove  some  ''  seed "  of 
sedge  from  a  ripened  head  and  study  its  structure.     As  you 

26 


THE    WIND    AS    A    SEED    DISTRIBUTER.  27 

pick  up  what  appears  to  be  the  seed  (Fig.  20)  you  notice  how 
little  Aveight  it  has.  On  looking  closer  you  are  likely  to  see 
that  it  is  triangular,  in  many  species  being  sha[)ed  like  a  minia- 
ture beechnut.  If  you  press  upon  it  the  ''seed"  breaks,  and 
you  find  it  apparently  hollow  on  the  inside.  But  if  you  look 
carefully  you  will  see  within  a  tiny  body  which  is  really  the 
seed.  The  other  is  simply  an  air-filled  boat  in  wliich  tlie  seed 
remains. 

A  seed  with  such  an  outer  covering  is  called  an  achene, 
although  in  most  achenes  there  is  not  the  air  space  which  tliese 
sedges  show. 

Now  drop  some  of  these  sedge  achenes  upon  the  surface  of 
water  in  a  tumbler  or  other  vessel. 
Do  they  sink  ?  See  them  rest  buo}'- 
antly  upon  the  top,  with  one  flat  side 
down  and  the  two  other  sides  pro- 
jecting upward.  Blow  gently  across 
the  water;  see  how  quickly  the  tiny 
sails  catch  the  breeze  and  the  achenes 
move  away.      Fancy    them    upon   a        fig.  20.  -  sedge  Achenes. 

quiet  pool  out  of  doors :  the  wind  ripples  the  surface  and  away 
they  go  to  the  other  side,  where  they  may  find  lodgment,  or, 
perchance,  if  the  pool  has  an  outlet,  they  may  be  carried  far 
away  by  the  running  water.  Either  contingency  fits  their 
needs :  if  the  water  is  quiet  they  ride  upon  the  surface  blown 
by  the  wind;  if  it  is  moving  they  are  carried  with  it.  It 
would  be  difficult  to  imagine  more  perfect  adaptation  to  sur- 
rounding conditions  or  simpler  means  of  attaining  it. 

The  forms  assumed  by  the  leaves  of  various  water  plants  are 
interesting  because  they  vary  so  greatly  in  different  kinds  of 
plants.  Few  leaves  are  more  striking  in  appearance  than  those 
of  the  arrow-leaf  which  grows  so  abundantly  along  the  bordei-s 


28 


SEED-TRAVELLERS. 


of  slow-runuing  streams,  as  well  as  along  the  margins  of  ponds 
and  marshes.  The  blossoms  of  the  larger  species  are  white 
and  conspicuous,  being  borne  on  good-sized  stalks  that  project 
above  the  surface  of  the  Avater.  The  fruits  are  developed  on 
these  stalks,  and  the  seeds  are  surrounded  by  thick,  air-filled 
tissues,  so  that  they  float  readily  upon  the  water. 

The  fruits  of  our  two  common  kinds  of  pond  lilies  are  also 
adapted  to  sailing  on  the  water.  In  the  case  of  the  white 
water  lily  —  Avhich  the  botanist  places  in  the  genus  Nymphcea 
—  "  each  seed  is  enveloped  in  a  coat  which  loosely  clothes  the 

outer  covering 
of  the  seed,  so 
as  to  leave  a 
layer  of  air 
between  the 
-^  ^    two." 


Fig.  21.  —  White  Water  Lilies. 


In  our  yellow  pond  lilies  —  belonging  to  the  genus  Nwphar 
—  there  are  two  layers  to  the  ripe  fruit,  "  of  which  the  outer 
one  is  green  and  succulent,  while  the  inner  one  is  white  and 
charged  with  air,  and  encloses  a  large  number  of  seeds."  The 
fruits  of  both  float  upon  the  water,  being  driven  over  the  sur- 
face by  the  wind  or  carried  by  the  motion  of  the  currents. 


PART   II.  — SEED   DISSEMINATION   BY   BIKDS. 


TRAVELLING   WITH   THE   BIRDS. 

In  tlie   struggle   for  existence  among   plants   and  animals, 
advantage  is  taken  of  all  sorts  of  conditions  that  may  aid  in 


p.itt. 


the  multiplication  of  the  species.  If  you  put  your  fingei-s  into 
a  tumbler  of  water  having  the  seed-like  achenes  of  a  sedge 
floating  on  the  surface,  and  then  withdraw  them,  you  are  likely 

29 


30  SEED-TRAVELLERS. 

to  find  one  or  more  of  the  achenes  attached  to  your  fingers. 
When  a  wild  duck  swims  around  upon  an  inland  pond  where 
these  sedge  fruits  are  floating,  it  comes  in  contact  with  many 
of  them  ;  when  it  rises  to  fl}^  to  another  pond,  perhaps  far  dis- 
tant, some  of  the  fruits  are  very  likely  to  adhere  to  the  feathers, 
remaining  in  position  until  the  duck  settles  in  a  pond  or  lake 
once  more,  when  they  will  again  float  upon  still  waters  new  to 
them.  In  this  way,  especially  during  the  spring  and  autumn 
migrations  of  waterfowl,  these  seeds  are  likely  to  be  dispersed 
over  wide  areas,  and  thus  be  constantly  introduced  into  new 
localities. 

These  sedge  achenes  must  finally  be  broken  up,  and  many  of 
the  tiny  seeds  within  the  husk  will  settle  in  the  mud  along  the 
borders  of  the  pond.  But  even  then,  the  possibilities  of  their 
dispersal  are  by  no  means  exhausted.  By  the  pondside  live  the 
herons  and  cranes,  the  snipes  and  sandpipers,  the  rails,  plovers, 
and  coots,  and  in  the  south  the  flamingoes  and  pelicans.  Here 
also  come,  especially  in  early  summer,  the  swallows  and  martins, 
the  robins  and  thrushes,  as  well  as  other  flying  birds  that 
seek  the  water  to  bathe  or  to  drink.  Nearly  all  of  these  birds, 
especially  the  larger  ones,  wade  in  the  mud,  and  when  they  fly 
more  or  less  of  it  must  adhere  to  their  feet  and  be  carried  to 
new  localities,  to  be  mixed  Avith  the  mud  of  other  pondsides. 
Thus  seed  distribution  of  sedges  and  other  water  plants  must 
take  place  to  a  great  extent  through  these  birds,  many  of  which 
are  known  to  fly  rapidly  over  long  distances. 

This  seems  a  very  simple  matter  now  as  one  reads  of  it,  but 
how  few  of  us  have  thought  of  it  as  we  saw  a  heron  rise  slowly 
from  the  margin  of  the  lake.  Like  a  thousand  other  things  in 
nature,  it  remained  unnoticed 

"  Till  one  who  sees  came  passing  by." 


SEED    DISSEMINATION    BY    IJlllDS.  31 

To  Darwin,  the  great  English  naturalist,  whose  genius  con- 
sisted largely  in  his  ability  to  see  the  significance  of  tlie  little 
things  in  life,  we  are  indebted  for  the  elucidation  of  this  metliod 
by  which  seeds  travel  with  the  birds.  jMany  years  ago  lie  reported 
the  following  simple  experiment,  which  may  easily  be  repeated 
in  any  schoolroom  :  "  I  do  not  believe,"  he  writes,  ''  that  botan- 
ists are  aware  how  charged  the  mud  of  ponds  is  with  seeds. 
I  have  tried  several  little  experiments,  but  will  here  give  only 
the  most  striking  case.  I  took  in  February  three  different 
tablespoonfuls  of  mud  from  three  different  places,  beneath 
water,  on  the  edge  of  a  little  pond.  This  mud  when  dry 
weighed  only  six  and  three-fourths  ounces.  I  kept  it  covered 
in  my  study  for  six  months,  pulling  up  and  counting  each  plant 
as  it  grew.  The  plants  were  of  many  kinds,  and  were  altogether 
five  hundred  and  thirty-seven  in  number;  and  yet  the  viscid  mud 
was  all  contained  in  a  breakfast  cup.  Considering  these  facts, 
I  think  it  would  be  an  inexplicable  circumstance  if  water  birds 
did  not  transport  the  seeds  of  the  same  fresh-water  plants  to 
unstocked  ponds  and  streams,  situated  at  very  distant  points." 
Additional  evidence  concerning  this  method  of  dispersal  has 
been  given  by  the  German  naturalist  Kerner,  who  examined 
the  mud  from  "the  beaks,  feet,  and  feathers  of  sA\'allows,  snipe, 
wagtails,  and  jackdaws,"  and  who  gives  a  list  of  twenty-one 
species  of  pondside  plants  whose  seeds  he  found  in  this  mud. 
*'  Most  of  these  species,"  Kerner  writes,  "  are  distributed  over 
all  parts  of  tlie  world,  but  they  seldom  remain  for  a  long  time 
in  any  particular  locality.  They  often  start  up  (juite  unex- 
pectedly at  places  where  migrating  birds  have  rested  and  gone 
to  drink.  The  extraordinary  occurrence  on  tlie  edges  of  ponds 
in  southern  Bohemia  of  the  tiny  grass  Colcauflius  subtil i.% 
which  is  indigenous  to  India,  and  the  sudden  appearance  of 
the  same  species  in  the  west  of  France  about  twenty  years  ago 


32  SEED-TKAVELLERS. 

may  unhesitatingly  be  attributed  to  this  mode  of  dispersion,  as 
may  also  the  occurrence  of  the  tropical  sedge  Scirpus  atropur- 
pureus  on  the  shores  of  the  Lake  of  Geneva." 

But  the  plants  of  the  water  side  are  not  the  only  ones  that 
travel  with  the  birds.  After  a  rain,  the  muddy  condition  of 
the  pond-shore  is  repeated  over  a  large  part  of  the  soil  surface. 
The  earth,  with  myriad  seeds  mixed  with  it,  is  sticky,  and 
adheres  to  the  feet  of  the  many  birds  that  light  upon  it,  as 
well  as  to  those  of  the  mammals  which  tread  over  it,  and  thus 
the  seeds  are  carried  hither  and  thither  in  every  direction. 
Many  of  our  commonest  weedy  plants  having  small  seeds  are 
distributed  in  this  manner. 


WILD   CHERRIES. 

Every  boy  who  has  lived  in  or  visited  tlie  country  in  Sep- 
tember knows  the  appearance  and  flavor  of  the  wild  black 
cherry.  This  tree  is  distributed  over  a  large  portion  of  the 
United  States,  and  is  found  most  abundantly  along  the  roadside 
fences.  In  size  it  varies  from  a  shrub  to  a  tall  tree,  with  the 
bark  smooth  and  shiny,  colored  brown,  mottled  witli  more  or 
less  gray.  The  leaves  are  oval,  smooth,  and  shiny,  light  green 
in  color,  and  have  finely  toothed  margins. 

In  May  the  beautiful  racemes  of  white  blossoms  appear  all 
along  the  smaller  twigs.  Each  raceme  is  a  tiny  branch  set 
apart  for  fruit  production.  It  bears  thirty  or  forty  of  the 
small  white  blossoms,  which  soon  pass  by,  to  be  replaced  in 
part  by  the  newly  formed  cherries.  These  are  small,  green, 
and  round,  each  being  borne  on  a  short  individual  stem 
attached  to  the  main  stem  of  the  raceme.  There  are  usually 
on  each  cluster  only  about  a  third  as  many  fruits  as  there  were 
blossoms. 

As  the  summer  daj^s  go  by,  the  cherries  slowly  increase  in 
size,  retaining  the  green  color  which  makes  them  inconspicuous 
among  the  green  leaves.  Late  in  summer  or  early  in  autunni 
each  cherry  becomes  full  grown,  having  a  diameter  of  a  little 
over  a  quarter  of  an  inch.  It  now  gradually  changes  color 
from  green  to  black.  When  fully  ripe  it  is  a  brilliant,  sliining 
black,  and  the  racemes  of  fruit  show  plainly  by  contrast  with 
the  light  green  foliage. 

Each  ripe  cherry  has  a  tliin  skin  covering  the  juicy  pulp  that 
surrounds  the  large  seed  in  the  center.     The  seed  lias  a  hard, 

33 


34 


SEED-TRAVELLEES. 


shell-like   covering,  within  which  is  the  white  seed  material 
that  contains  the  embryo  plant. 

These  cherries  are  eaten  by  many  birds  and  are  largely  dis- 
seminated by  them.  Even  so  large  a  bird  as  the  crow  feeds 
freely  upon  them,  while  various  members  of  the  thrush  family, 
such  as  the  robin,  the  brown  thrush,  and  the  catbird,  make  of 


Fig.  23.  —  The  Common  Crow.    (After  Barrows.) 

the  cherries  one  of  the  most  important  parts  of  their  food  dur- 
ing the  early  autumn. 

The  cherries  are  taken  into  the  crops  of  these  birds.  The 
edible  pulp  that  surrounds  the  pit  is  digested,  while  the  hard 
seeds  are  either  thrown  up  through  the  mouth  or  pass  through 
the  alimentary  canal.  In  either  case  they  fall  to  the  ground, 
frequently  after  having  been  carried  some  distance  from  the 
tree  on  which  they  grew,  and  in  due  time  many  of  them  ger- 
minate and  grow  into  trees. 


THE   POKEBERRY,    OR   POKEWEED. 

In  many  places  throughout  the  northern  states,  especially 
in  recent    clearings  in   woodlands,  the    pokel)erry,   poke  weed. 


Fig.  24.  —  The  P()kt'l)erry. 


or  garget,  is  one  of  the  most  familiar  autumn  ] Hants.  Grow- 
ing generally  in  masses,  to  a  height  of  four  or  live  feet,  tlie 
plant  is  conspicuous  on  account  of  its  purplish  red  stems,  liglit 


35 


36 


SEED-TRAVELLEKS. 


yellowish  green  leaves,  and  long  bunches  of  brilliant,  black 
purple  berries  (Fig.  24). 

These  berries  are  arranged  all  around  the  central  stem,  there 
being  about  fifty  berries  in  each  mass.  The  ripest  and  blackest 
fruits  are  at  the  base  of  the  stem,  those  at  the  tip  ripening  last. 
In  September  a  single  fruit-bunch  will  show  the  various  shades 
from  green  through  purple  to  black,  which  characterize  the 
ripening  process. 

Each  berry  suggests  by  its  shape  a  miniature  apple  somewhat 


Fig.  25  —  The  Mocking  Bird.     (After  Beal.) 

flattened  on  the  ends.  The  remnants  of  the  pistils  project  as 
a  circle  of  small  pointed  spurs  on  the  top.  If  you  break  open 
the  skin,  you  find  on  the  inside  a  juicy  purple  pulp,  in  which 
are  imbedded  nearly  a  dozen  small,  black,  flattened  seeds. 
Inside  the  black  seed-coat  of  each  is  the  white  material  sur- 
rounding the  tiny  embryo  plant. 

The  pokeberries  remain  upon  the  stems  a  long  time  after  the 
frost  has  chilled  the  leaves.     The  berries  are  eaten  by  cedar 


SEED   DISSEMINATION    BY    BIRDS. 


37 


birds,  crows,  blackbirds,  robins,  and  many  other  members  of  tlie 
feathered  tribes.  In  the  southern  states  the  famous  mocking 
bird  feeds  upon  them,  as  well  as  upon  the  seeds  and  berries  of 
many  other  plants,  such  as  poison  ivy,  Virginia  creeper,  sumach, 
red  cedar,  black  alder,  and  bayberry.  The  German  naturalist 
Kerner  reports  that  "a  song  thrush  sickened  after  eating 
berries"  of  the  poke  weed,  but  there  seems  to  l)e  little  evidence 


fjW^t 

..  -  '"^l 

,.«v-  — 

^#. 

&%s. 

Fig.  26.  —  The  Cedar  Bird. 

to  indicate  that  the  berries  are  injurious  to  the  wild  birds  that 
feed  upon  them  here.  The  seeds  are  so  small  and  hard  that 
they  probably  pass  through  the  alimentary  canals  of  the  birds 
without  being  digested. 

The  situations  in  Avhicli  the  pokeweed  is  most  abundant  — 
along  roadsides  and  in  clearings  in  woods  —  are  suggestive  of 
dissemination  by  birds,  for  these  are  the  places  where  one  is 
most  likely  to  find  the  fruit-eating  songsters. 


THE   BARBERRY. 


The  barberry  is  another  fruit  that  is  attractive  to  birds.  All 
along  the  coast  region  of  New  England,  and  in  many  other 
localities  inward,  this  handsome  shrub  is  found  in  abundance, 


I'lG.  2,".  — Branches  of  Barberries. 

while  all  over  the  country  it  is  commonly  planted  in  parks  and 
grounds  for  its  ornamental  value.  It  is  beautiful  throughout 
the  year,  especially  in  early  summer  when  the  graceful  racemes 
of  light  yellow  flowers  form  a  pleasing  color  harmony  with  the 
blue  green  leaves,  and  in  autumn  when  the  drooping  clusters  of 
brilliant  red  berries  add  a  unique  charm  to  the  landscape. 

If  you  break  open  the  skin  of  one  of  the  barberry  fruits,  you 
will  find  inside  a  red  pulp  that  surrounds  a  brown  seed,  some- 
what the  shape  of  an  apple  seed,  although  it  is  not  flattened 


SEED    DISSEMINATION    V,Y    BIRDS.  39 

SO  much  upon  the  sides.  These  berries  are  eaten  Ijy  many 
different  kinds  of  birds,  which  scatter  the  seeds  in  every  direc- 
tion. In  the  case  of  most  of  the  smaller  birds  that  feed  upon 
the  berries,  the  seeds  are  probably  ejected  through  tlie  mouth 
after  the  pulp  has  been  digested.  The  fact  that  the  l)arljerries 
hang  upon  the  bushes  from  autumn  until  spring,  always  ready 
to  be  eaten  by  any  feathered  vagrant,  even  Avhen  the  snow 
covers  other  kinds  of  food,  is  of  great  advantage  to  the  plant. 


THE   POISON  IVY  AND   THE   HARMLESS   SUMACHS. 

The  poison  ivy  is  everywhere  abundant,  and  is  an  interest- 
ing example  of  a  plant  whose  seeds  are  dispersed  by  birds.  The 
pretty,  compound,  three-parted  leaves  of  this  plant  are  only  too 
familiar  to  many  people  susceptible  to  the  subtle  poison  that 
I'enders  contact  with  the  vines  a  matter  of  serious  concern. 
Others,  however,  can  handle  the  leaves  and  fruits  with  im- 
punity. 

As  autumn  weaves  the  brilliant  web  of  her  showy  garment, 
she  uses  the  poison  ivy  and  the  Virginia  creeper  to  fill  in  large 
masses  of  deep  crimson  tones,  that  form  a  pleasing  color  har- 
mony with  the  yellows  and  browns  of  the  low-lying  herbage. 

More  or  less  hidden  by  the  foliage  of  the  ivy  are  the  white 
berries  which  form  its  fruit.  They  are  borne  in  broken  racemes 
on  slender  stems.  Each  berry  is  globular,  though  more  or  less 
irregular.  As  you  break  it  open  you  find  on  the  outside  the 
brittle  white  skin,  inside  of  which  is  a  whitish  firm  substance, 
closely  connected  with  the  seed-coat  of  the  fruit.  This  seems  as 
unpromising  a  "  berry "  as  one  well  could  imagine,  yet  on 
account  of  the  dryness  of  what  stands  in  place  of  the  pulp  of 
other  berries,  it  will  keep  through  the  winter  in  as  good  con- 
dition as  when  it  first  matures. 

This  is  its  method  of  adapting  itself  to  the  conditions  of 
life.  During  late  summer  and  throughout  autumn  the  birds 
are  able  to  get  raspberries,  blackberries,  grapes,  wild  cherries, 
and  other  succulent  fruits.  These  pass,  however,  with  the 
season,  and  during  the  period  when  Mother  Earth  is  shrouded 
in  a  snowy  mantle,  the  birds  fall  back  upon  these  better-keep- 


SEED    DISSEMINATION    liV    P.IRDS. 


41 


ing  fruits  for  sustenance.  From  October  to  February  tbe 
crows,  for  example,  feed  freely  upon  the  berries  of  poison  ivy, 
there  being  one  case  on  record  in  which  one  hundred  and  fifty- 
three  of  these  seeds  were  taken  from  the  stomach  of  a  single 
crow.     Soon  after  the  seeds  are  swallowed  the   outer  part  is 


Fig.  28.  — The  Red  Sumach  IJerri 


removed  by  the  action  of  the  stomacli,  and  the  seeds  are  tlirown 
out  through  the  mouth  of  the  bird,  in  "  pellets  "  similar  to  the 
one  represented  in  Fig.  30. 

Botanically,  the  poison  ivy  is  a  sumach  belonging  to  the 
genus  Blms^  that  includes  the  common  harmless  sumachs,  the 
most  abundant  of  which  is  represented  in  Fig.  28.  This,  too, 
is  largely  used  in  autumn's  gail}^  colored  woof;  liere  and  there 
it  lies  in  solid  patches  of  crimson  and  maroon,  —  glowing  coloi-s 
that  add  much  beauty  to  hillside  and  wayside. 


42 


SEEDta:RAVELLE>ES. 


These  harmless  sumachs  are  produced  in  large  panicles  on 
the  ends  of  the  branches.  When  mature  they  are  of  a  deep 
maroon  color.  As  one  examines  them  individually,  they  seem 
as  food  supplies  even  less  promising  than  the  berries  of  the 
poison  ivy.  The  birds,  apparently,  are  also  of  this  opinion,  for 
in  general  they  leave  these  berries  until  other  sources  of  food 


Kougli-leaved  Cornel 
{Co7mus  asperifolia) 


Catbrier 
{Smilax  rotundi/olia) 

Smooth  Sumach 
(Ehus  glabra) 


Flowering  Dogwood 
{Co7-mts  florida) 


Poison  Sumach 
(lihus  riiwnata) 


^      <Q)       ^ 


Sour  Gum 
(^yssa  aquatica) 

Fig.  29.  —  Seeds  Eaten  by  Crows.    (After  Barrows.) 


Poison  Ivy 
(Rhus  toxicodendron) 


are  exhausted.  Even  the  crows  wait  until  winter  before  they 
feed  freely  upon  them.  A  number  of  birds,  the  catbird,  for 
example,  eke  out  the  slender  diet  of  early  spring  with  these 
berries. 

A  few  years  ago  Prof.  Walter  B.  Barrows  made  a  careful 
study  of  the  food  of  the  crow.  He  discovered  many  inter- 
esting facts  in  connection  with   the   life  history  and  feeding 


SEED    DISSEMINATION    BY    lilltDS.  43 

habits  of  these  birds,  pai-ticuhirly  Avith  lul'ciciicc  to  tlic  ciow 
*' roosts."  These  are  [)hiees  where  iniineiise  iiuinbers  of  crows 
congregate  every  night.  Regarding  the  dispersal  of  seed  in 
the  vicinity  of  these  roosts,  Professor  Barrows  writes : 

"The  following  facts  serve  to  show  how  extensive  is  this 
seed-planting  in  the  vicinity  of  roosts:  On  Feb.  8,  1889, 
I  visited  the  well-known  —  almost  historical  —  crow  roost 
located  on  the  Virginia  side  of  the  Potomac  River,  jnst 
opposite  Washington,  D.  C.  The  exact  location  of  this  roost 
varies  from  time  to  time,  but  at  the  date  mentioned  it  was 
entirely  within  the  grounds  of  the  National  Cemetery  at 
Arlington,  and  covered  an  area  of  twelve  or  fifteen  acres  of 
second-growth  deciduous  trees.  The  ground  beneath  these 
trees  was  pretty  evenly  covered  with  the  ejects  of  the  crows, 
forming  a  deposit  which  in  places  was  an  inch  or  more  thick, 
though  the  average  deposit  was  probably  less  than  half  an  inch. 
A  representative  spot,  free  from  underbrush,  was  selected,  and 
all  the  material  above  the  leaves  from  an  area  two  feet  square 
was  carefully  collected,  dried,  and  examined.  The  Aveight  of 
this  material  when  dry  was  almost  exactly  one  pound,  and  it 
contained  the  following  seeds : 

Number. 

Poison  ivy  (Rhns  toxicodendron^ 1041 

Poison  sumach  (Rhus  venenaUi) 3-il 

Other  sumachs  (Rhus) 3271 

Juniper,  or  red  cedar  {Juniperus  vlrglniana)    .     .  05 

Flowering-  dogwood  (Corniis  Jiorida)      ....  10 

Sour  gum  (Nyssa  aquatica) 6 

Total 4764 

"A  little  calculation  shows  that  the  roost  of  fifteen  acres 
must  have  contained  upward  of  778,000,000  seeds,  or  more 
than  enough  to  plant  1150  acres  as  thickly  as  wheat  is  sown. 


44 


SEED-TflAVELLERS. 


"  Of  course  the  seeds  thus  dropped  at  the  roost  are  subject 
to  such  unfavorable  conditions  that  comparatively  few  grow, 
but  it  must  be  remembered  that  crows  spend  only  the  hours  of 
darkness  at  the  roosts,  while  during  at  least  twelve  hours  each 
day  they  are  disj^ersed  far  and  wide  over  the  surrounding 
country,  collecting  and  distributing  these  seeds.  The  process 
of  digestion  —  at  least  the  preliminary  process  —  is  very  rapid 
A    caged   crow,  experimented   on   during   several 


m    crows. 


Fig.  30.  —  CroAY  Pellet.     (After  Bakrows.) 

months  in  the  winter  of  1889-90,  ate  berries  of  poison  ivy 
with  greater  relish  than  any  other  wild  fruit  obtainable.  He 
swallowed  about  eighty  berries  within  a  few  moments,  taking 
several  mouthfuls  of  sand  immediately  afterwards;  and  about 
thirty  minutes  later  he  disgorged  a  large  pellet,  consisting 
entirely  of  sand  and  the  seeds  of  the  poison  ivy  berries,  the 
latter  with  every  shred  of  pulp  removed  by  the  gizzard-like 
action  of  the  stomach." 


PAET  III,  —  SEP:D  dispersal  BY  SPINES  AND  HOOKS. 


THE   BURR   MARIGOLD   AND   THE   HOOKED   CROWFOOT. 

The  burr  marigold  is  one  of  the  most  characteristic  autumn 
plants.  Along  the  roadsides,  in  the  ditches,  or  by  the  borders 
of  the  pond  one  is  quite  certain  to  find  the  large  bright  yellow 
blossoms  crowning  the  double-branching  stems.  At  the  base 
of  each  flower  head  there  is  a  double  circle  of.  large  green 
bracts,  the  outer  being  larger  and  more  conspicuous  than  the 
inner.  Like  the  dandelion,  the  thistle,  and  the  sunfloAver,  the 
burr  marigold  belongs  to  the  family  of  composite  plants,  in 
which  many  tiny  flowers  are  crowded  together  into  a  single 
head,  so  that  what  we  commonly  tliink  of  as  the  blossom 
really  consists  of  many  individual  flowers. 

Inside  the  ring  of  green  bracts  there  is  a  row  of  yellow 
petal-like  objects,  which  give  the  blossom  its  chief  attractive- 
ness ;  remove  these  and  the  flower  head  becomes  inconspicuous. 
These  are  the  so-called  ray  flowers ;  the  remainder  are  the  disk 
flowers.  Pull  tlie  blossom  apart  and  you  Avill  see  that  the 
individual  disk  flowers  have  a  general  cylindrical  appearance, 
with  the  seed-bearing  part  —  called  the  ovar}^  —  at  the  base. 
In  some  of  the  older  blossoms  which  are  becoming  brown, 
notice  that  these  ovaries  have  developed  into  Avhat  we  com- 
monly call  the  seed. 

Look  at  one  of  these  seeds  through  a  simple  lens,  and  study 
its  structure.  See  the  four  ribs  extending  up  and  down  along 
the  sides,  and  notice  particularly  the  sharp-pointed  hooks  curv- 

45 


Fig.  31.— Pitchforks,  or  Beggar  Ticks.    (After  Coville.) 


SEED    DISPERSAL    BY    SPINES    AND    HOOKS. 


47 


ing  backward  toward  the  base.     See  how  these  ribs  project  up 
beyond  the  seed,  as  spines  provided  with  recurved  barbs. 

In  pulling  the  seed-head  to  pieces,  some  of  these  seeds  are 
likely  to  adhere  to  the  fingers  by  means  of  these  barbs,  while 
if  you  touch  them  to  a  piece  of  cloth  tliey  will  ''  stick  tight,"  — 
a  fact  which  has  given  them  this  term  for  a  common  name. 
It  is  easy  to  see  how  this  sort  of  an  adaptation  would  be  useful 
to  the  plant  in  getting  its  seed  dispersed. 


Fig.  32.  -Aclienes  of  Beggar  Ticks,  Miignitied. 

Instead  of  calling  upon  the  wind  to  waft  its  seeds  far  and 
wide,  it  makes  the  beasts  of  the  field  its  burden-bearers. 
These  "  stick-tights  "  will  take  firm  hold  upon  the  hair  or  fur 
of  almost  any  of  the  larger  animals,  many  of  which  under  the 
conditions  existing  in  previous  ages  of  tlie  world,  Avhen  our 
plants  were  developing,  roamed  about  in  just  the  situations 
where  the  burr  marigold  is  most  at  home.  So,  also,  they  do 
to-day,  though  mankind  has  interfered  in  the  older  settled 
regions  to  render  communication  by  such  animals  between 
regions  far  apart  more  difficult  than  formerly. 


48  SEED-TRAVELLERS. 

Besides  the  common  burr  marigold  there  are  several  other 
species  of  plants  belonging  to  the  same  genus  that  have  adopted 
similar  methods  of  seed  dispersal.  Perhaps  the  most  abundant 
of  these  are  the  common  "beggar  ticks,"  or  ''pitchforks,"  in 
which  the  achenes  (Fig.  32)  have  two  pointed  projections,  called 
awns,  and  the  Spanish  needles,  in  which  the  achenes  are  larger 
and  have  three  or  four  awns. 


Fig.  33.  — Hooked  Achenes  of  Crowfoot,  Mjignified. 

Along  the  borders  of  woods  one  can  commonly  find  in 
autumn  the  peculiar  seed-heads  of  the  hooked  crowfoot.  The 
individual  achenes  of  this  plant  are  represented,  enlarged,  in 
Fig.  33.  In  each  the  seed-coat  is  prolonged  into  a  short  stalk 
that  ends  in  a  recurved  hook.  These  achenes  are  crowded 
together  into  a  small  round  head,  and  readily  take  hold  upon 
the  hair  of  any  animal  that  may  brush  against  them. 


THE   BURDOCK  AND   THE   CLOTBURR. 

In  the  burr  marigold  each  acheiie  is  provided  with  hooks  to 
assist  in  its  dissemination,  but  in  the  case  of  the  common  bur- 
dock the  hooks  are  on  the  outside  of  the  seed-head,  while  the 
seeds  themselves  are  quite  smooth. 

If  you  examine  a  burdock  blossom  you  will  find  the  lower 
part  of  the  flower  head  covered  with  green  scales,  each  of  wliich 
projects  upward  and  outward,  and  at  the  tip  curves  over  into 
a  sharp-pointed  hook,  much  the  shape  of  a  fishhook.  As  the 
flower  matures  these  hooks  gradually  become  dry.  Finally, 
when  the  seeds  are  ripe,  the  hooks  are  ready  to  catch  hold  of 
any  animal  that  brushes  against  the  plant. 

By  this  time  the  connection  with  the  stem  at  the  base  of  the 
flower  head  has  become  sufficiently  loosened  so  that  the  burr 
pulls  off  readily.  Yet  it  holds  on  tight  enough  to  remain 
attached  to  the  plant  through  the  winter,  unless  the  grappling 
hooks  are  taken  hold  of  by  some  external  agency.  Conse- 
quently, the  period  during  which  the  seeds  are  open  to  dis- 
semination extends  over  many  months.  This,  of  course,  is  a 
decided  advantage,  for  it  greatly  increases  the  chances  tliat  tlie 
seeds  will  be  carried  to  other  localities. 

When  the  burr  becomes  attached  to  the  hair  of  an  animal,  it 
may  be  some  time  before  it  is  removed.  As  it  is  rubbed  by  the 
creature  or  is  brushed  against  trees  or  branches,  it  is  likely  to 
be  pushed  open,  and  the  dozen  or  more  seeds  are  likely,  one  by 
one,  to  drop  to  the  ground.  The  individual  seeds  are  rather 
large,  in  color  brown  mottled  with  l)lack,  and  rather  smooth 
exce^^t  for  a  few  slightly  projecting,  longitudinal  ridges. 

49 


Fig.  34.  —  The  Common  Burdock. 


SEED    DISPERSAL    BY    Si'lNES    AND    HOOKS.  51 

The  seed-heads  of  the  common  clotburr  (Fig.  3G)  of  waste 
grounds  are  very  simihxr  in  general  structure  to  those  of  the 
burdock,  as  will  be  seen  by  referring  to  Fig.  34.  The  burrs 
are  oblong,  about  an  inch  long,  with  two  large  spiny  hooks  at 
the  tip,  and  many  smaller  hooks  scattered  over  the  surface. 
They  get  into  the  avooI  of  sheep,  whence  they  are  not  easily 
dislodged,  so  that  when  the  wool  is  cut  off  and  shipped  to  dis- 
tant regions,  these  burrs  are  often  carried  with  it. 

An  idea  of  the  important  part  played  by  these  various  hooks 
and  spines  in  the  dissemination  of  seeds  may  be  gained  by 
reading  the  following  paragraph  written  by  the  German  bot- 
anist Kerner: 


Fig.  35.  —  Seeds  of  Burdock. 

"About  ten  per  cent  of  all  the  flowering  plants  possess 
fruits  and  seeds  which  are  dispersed  by  means  of  clawed  or 
barbed  processes.  The  part  of  the  plant  which  is  provided 
with  these  structures  hooks  on  to  the  hairs,  bristles,  or  feathers 
of  any  bird  or  other  animal  that  happens  to  come  into  contact 
with  it.  The  consequence  is  that  it  is  torn  away  and  carried 
off  by  the  animal.  This  act  of  depredation  is,  of  course,  not 
intentional  on  the  part  of  the  creature  that  performs  it ;  on  the 
contrary,  such  appendages  are  a  source  of  discomfort,  and  are 
got  rid  of  as  soon  as  possible.  But  in  many  cases  this  is  not 
accomplished  until  a  considerable  distance  has  been  traversed. 


Fig.  36.  —  Clotburr  :  1,  Plant  in  Blossom  ;  2,  Burrs.    (After  Vasey.) 


SEED    DlSPEllSAL    BY    SPINES    AND    HOOKS.  53 

and  sometimes  the  troublesome  objects  remain  for  weeks  in  tlie 
creature's  coat  or  mane.  The  organs  of  attachment  are  either 
hooked  at  the  tip  or  beset  with  barbs.  In  the  latter  case,  the 
barbs  are  borne  on  special  rigid  bristles  or  needles,  and  are 
either  collected  together  at  the  top  as  in  a  harpoon  or  else  are 
arranged  in  longitudinal  rows  as  in  a  hackle  for  combing  flax. 
Only  in  a  few  instances  do  these  structures,  which  may  be 
classed  together  as  hooked  bristles  and  hooked  prickles,  occur 
on  the  seeds  themselves ;  usually  they  are  appendages  of  the 
seed-coat,  and  as  such  exhibit  every  degree  of  size  possible, 
from  the  delicate  hooked  bristles  on  the  small  nutlets  of  the 
enchanter's  nightshade-  to  the  thick,  firm  claws  of  the  African 
harpoon  fruit.  The  hooked  spines  of  the  latter  fruits  attain 
the  size  of  crows'  feet,  and  are  a  notorious  source  of  vexation 
to  ruminant  animals,  both  wild  and  tame."  ^ 

1  Natural  History  of  Plants,  II,  871. 


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